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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

28221 results found.

  1. GRB 251001A: Fermi GBM Detection
  2. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  3. GRB 251001A: Fermi GBM Final Real-time Localization
  4. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  5. GRB 250925A: MAO/AZT-22 optical observations
  6. GRB 250929A: Fermi GBM Final Real-time Localization
  7. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  8. GRB 250925A: Mondy I-band optical observations
  9. GRB 250924A: SVOM/GRM observation
  10. GRB 250925A: Swift-XRT refined Analysis
  11. GRB 250926A: Insight-HXMT detection
  12. GRB 250926B: Fermi GBM Final Localization
  13. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  14. GRB 250926A: AstroSat CZTI detection
  15. GRB 250925A: Swift/UVOT Upper Limits
  16. GRB 250925A: Mondy and AbAO optical observations
  17. GRB 250925A: COLIBRÍ photometric redshift
  18. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 250925A: SVOM/GWAC-F60A upper limit
  20. GRB 250925A/EP250925a: EP-WXT detection
  21. GRB 250925A: JinShan optical observations
  22. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  23. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  24. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  25. GRB 250926A: Fermi GBM Final Real-time Localization
  26. GRB250925A: Liverpool Telescope optical observations
  27. GRB 250925A: NOT optical afterglow candidate
  28. GRB 250925A: Enhanced Swift-XRT position
  29. GRB 250925A: Swift detection of a burst
  30. GRB 250924A: 1.6m Mephisto optical upper limits
  31. GRB 250924A: NOT optical observations
  32. GRB 250924A: AstroSat CZTI detection
  33. GRB 250914A: AstroSat CZTI detection
  34. GRB 250920B: AstroSat CZTI detection
  35. GRB 250924A: Swift/UVOT Detection
  36. GRB 250924A: Swift-XRT refined Analysis
  37. GRB 250924A: Enhanced Swift-XRT position
  38. GRB 250924A: J-band detection with WINTER
  39. GRB 250924A: KAIT optical observations
  40. GRB 250924A: Mondy optical observations, afterglow fading
  41. GRB 250924A: Kilonova-Catcher optical afterglow detection
  42. GRB 250920C: Kilonova-Catcher optical afterglow detection
  43. GRB 250920C: TRT optical observation
  44. GRB 250924B: Fermi GBM Final Localization
  45. GRB 250919A / EP250919a: further LCO optical observation
  46. GRB 250924A: DDOTI Detection of the Optical Counterpart
  47. GRB 250924A: Swift detection of a burst with an optical counterpart
  48. GRB 250920B: AbAO optical upper limits
  49. Konus-Wind detection of GRB 250920C
  50. GRB 250920C: KAIT optical observations
  51. GRB 250920C: VLT redshift confirmation z = 1.399
  52. GRB 250920B: CrAO ZTSH optical observations
  53. GRB 250920C: SALT redshift confirmation
  54. GRB 250920C: COLIBRÍ optical observations
  55. GRB 250922C: AstroSat CZTI detection of a short burst
  56. GRB 250922B: Fermi GBM Final Real-time Localization
  57. GRB 250920C: PRIME near-infrared detection
  58. Konus-Wind detection of GRB 250920B
  59. Konus-Wind detection of GRB 250920A
  60. IPN triangulation of GRB 250920A (long/bright)
  61. Konus-Wind detection of GRB 250911A
  62. GRB 250916A: Swift/UVOT Detection
  63. GRB 250920B: Glowbug gamma-ray detection
  64. GRB 250920C: Swift-XRT refined Analysis
  65. GRB 250922A: Fermi GBM Final Localization
  66. GRB 250920B: Kitab-ISON optical upper limit
  67. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  68. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  69. GRB 250917B: KAIT optical upper limit
  70. GRB 250920A: NuSTAR detection of bright prompt emission
  71. GRB 250920C: GROWTH-India Telescope optical observations
  72. GRB 250920C: Enhanced Swift-XRT position
  73. GRB 250920C: Swift/UVOT Detection
  74. GRB 250920A: Fermi GBM Detection
  75. GRB 250920B: Swift/UVOT Detection
  76. GRB 250920C: Optical counterpart detection by LCO
  77. GRB250920C: LCOGT Optical Detection
  78. GRB 250920B: Enhanced Swift-XRT position
  79. GRB 250920B: Swift-XRT refined Analysis
  80. Konus-Wind detection of GRB 250919A
  81. GRB 250920C: Swift detection of a burst
  82. GRB 250920C: Fermi GBM Final Real-time Localization
  83. GRB 250919A / EP250919a: Insight-HXMT detection
  84. GRB 250920A: AstroSat CZTI detection
  85. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  86. GRB 250920B: Fermi GBM Final Real-time Localization
  87. GRB 250920A: Fermi GBM Final Localization
  88. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  89. GRB 250916A: Mondy R-band optical observations
  90. GRB 250919A: Glowbug gamma-ray detection
  91. GRB 250919A: Fermi GBM Observation
  92. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  93. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  94. GRB 250919A: Swift-XRT afterglow detection
  95. GRB 250919A: Fermi-LAT detection
  96. EP250919a: Einstein Probe detection of an X-ray transient
  97. GRB 250919A: Fermi GBM Final Real-time Localization
  98. GRB 250916A: KAIT optical observations
  99. GRB 250916A: NuSTAR detection of the prompt emission
  100. GRB 250918A: Fermi GBM Final Real-time Localization

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